Studies will be conducted to examine the intestinal epithelial mechanisms of fluid loss in infantile soybean protein (SBP) intolerance. Preliminary studies have demonstrated that SBP-intolerance is characterized by enhanced secretion in the jejunum. We have hypothesized that this arises from an interaction between SBP and galactosyl or galactosaminyl receptors on the surface of susceptible villus cells. The existence of such receptors might be due to deficient sialyltransferase activity. The presence of a secretory state during periods of SBP feeding and its correction by galactosides will be investigated by the luminal perfusion technique. The lectin effect of purified SBP (glycinin) will be studied in mucosal explants obtained by per oral small bowel biopsy. The agglutinating effect will be assessed morphologically and the mitotic effect by quantitation of 3H-thymidine uptake. The binding of labeled glycinin and its inhibition by galactosides will be studied in intestinal cell suspensions from susceptible mucosal tissues. A rabbit model of SBP-intolerance will be developed by neuraminidase desialylation of mucosal tissues in vivo.